| 摘要 |
This high-pressure, high-temperature anhydrous process prepares melamine from urea. It is a primary object of the present invention to provide a highly energy-efficient and improved continuous process for the production of melamine from urea which utilizes a simplified process to produce and recover a high-grade (96 to 99.5% purity) melamine as a dry powder directly from liquid melamine melt. Molten urea is supplied to a reactor maintained at high temperature (700 DEG to 800 DEG F.) and high pressure (1700 to 2200 psig) whereby melamine, CO2, and NH3 are formed. The reactor effluent stream containing liquid melamine, CO2, and NH3 is transferred to a gas separator where CO2 and NH3 containing melamine are separated and cycled to a scrubber unit for scrubbing with molten urea reactant to remove the melamine before transfer of the CO2 and NH3 gases at high pressure to an adjacent urea plant for utilization in producing urea. The melamine liquid product is transferred from the gas separator to a collecting tank maintained at a pressure of less than about 615 psig and from about 120 DEG to 260 DEG F. where the liquid melamine is immediately contacted with, or quenched with a liquid, preferably liquid ammonia. The melamine separates as a dry powder which requires no further processing, having a purity in the range of 96 to 99.5%, useful in applications including fertilizer and resin manufacture. This process is highly cost efficient.
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